ULA Delta IV launches WGS-8 satellite

United Launch Alliance (ULA) has launched a Delta IV rocket on Wednesday evening, carrying the eighth satellite in the US Air Force’s Wideband Global Satcom system. The rocket lifted off with WGS-8 from Cape Canaveral Air Force Station’s SLC-37B pad at 18:52 Eastern Time (23:52 UTC).

WGS was originally devised as an interim program to augment and replace Defense Satellite Communications System (DSCS) spacecraft, providing additional bandwidth ahead of the deployment of a constellation of high-performance Transformational Satellite (TSAT) spacecraft.

Until 2007, WGS stood for Wideband Gapfiller Satellite. The program’s role had already begun to expand before TSAT was canceled in 2009 in favor of additional WGS and Advance Extremely High Frequency (AEHF) satellites.

The WGS satellites are far more capable than their DSCS predecessors; a single Wideband Global Satcom spacecraft has more communications bandwidth than the entire DSCS constellation. WGS spacecraft carry transponders operating in the X and Ka bands of the electromagnetic spectrum.

WGS satellites are constructed by Boeing, who were awarded an initial contract in 2001 for two satellites and an option for a third, with launches scheduled to begin in 2004. The contract option was converted to an order for a third satellite in early 2003.

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The Air Force ordered fourth and fifth satellites in November 2006, while the Australian government funded the addition of a sixth satellite in October 2007, in exchange for use of the constellation.

Four follow-on satellites, WGS-7 to 10, were contracted between September 2011 and July 2012, with WGS-9 being funded through contributions from Canada, Denmark, Luxembourg, the Netherlands and New Zealand as the program gained further international partners.

The first launch of the WGS program took place on 11 October 2007, with an Atlas V 421 deploying the WGS-1, or USA-195, satellite into geosynchronous transfer orbit. The second satellite was also deployed by Atlas, in April 2009. All subsequent launches have used Delta IV rockets, in the Medium+(5,4) configuration. WGS-3, or USA-211, was successfully launched in December 2009.

The first three satellites were Block I spacecraft; subsequent spacecraft were built to the Block II standard with a radio frequency bypass modification to provide additional high-bandwidth support for unmanned aerial vehicles. The WGS-4, 5, 6 and 7 satellites were launched in January 2012, May and August 2013 and July 2015 respectively.

The second Block II Follow-On (B2FO) satellite, WGS-8 will be the first satellite to debut an upgrade to the Wideband Digital Channelizer, which is expected to increase the spacecraft’s throughput; raising its maximum data bandwidth from around 6 gigabits per second (Gbps) to up to 11 Gbps.

Wideband Global Satcom spacecraft are based around Boeing’s BSS-702HP satellite bus. Operating in geosynchronous orbit, each spacecraft has a design lifespan of fourteen years. Fuelled, the satellite has a mass of 5,987 kilograms (13,200 lb). In 2012, the cost of the WGS-8 spacecraft was estimated at $353.9 million.

United Launch Alliance (ULA) was responsible for conducting Wednesday’s launch. Using a Delta IV Medium+(5,4) rocket flying from Space Launch Complex 37B at the Cape Canaveral Air Force Station in Florida, the mission lasted forty-one minutes and 43.6 seconds from liftoff to spacecraft separation.

The launch of WGS-8 comes a week after ULA celebrated its tenth anniversary; the company was founded on 1 December 2006 through the amalgamation of the launch vehicle divisions of Lockheed Martin – the original manufacturer of the Atlas V – and Boeing, who developed the Delta IV and also manufactured the earlier Delta II.

ULA took over the production and launch operations of both Deltas and the Atlas, its first launch occurring on 14 December 2006 when a Delta II orbited the NROL-21 mission, the ill-fated USA-193 satellite. Despite a successful launch, the spacecraft failed immediately after separating from its carrier rocket. In February 2008, the US Navy used a Standard Missile 3 (SM-3) missile to destroy the non-functional satellite, which was about to re-enter the atmosphere.

In its first decade of operations, United Launch Alliance conducted 113 launches – Wednesday’s launch is its 114th mission – with a near-perfect record. The only launch which failed to achieve its planned orbit was of an Atlas V in June 2007, which placed a pair of National Reconnaissance Office ocean surveillance satellites, NROL-30, into a lower-than-planned orbit after a faulty valve caused an upper stage propellant leak.

Despite the anomaly, the satellites were able to maneuver to the correct orbit under their own power. ULA and the National Reconnaissance Office characterize the launch as successful, however independent analysts regard it as a partial failure.

The WGS-8 launch was the thirty-fourth flight of the Delta IV, and the twenty-seventh of these to be conducted by United Launch Alliance. The remainder of ULA’s launches have been made by twenty-eight Delta II vehicles and 59 Atlas V rockets. As a provider of launch services to the US Government, ULA’s main customers have been the US military and NASA.

The company has launched seventeen navigation satellites for the Global Positioning System constellation, including both older Block IIRM spacecraft atop Delta II rockets, and the entire Block IIF series using Atlas V and Delta IV vehicles. Two Defence Meteorological Satellite Program (DMSP) military weather satellites were launched using Atlas V rockets in 2009 and 2014.

Missile detection which ULA’s rockets have deployed have included the final Defense Support Program (DSP) satellite and the first two vehicles of the successor Space Based Infrared System (SBIRS) geosynchronous program. A pair of Space Tracking and Surveillance System (STSS) spacecraft were deployed by a Delta II in September 2009, while an associated demonstration mission was launched earlier the same year.

Twenty-three launches have been made in support of National Reconnaissance missions, with payloads including optical and radar imaging satellites, ocean surveillance missions, geosynchronous and eccentric-orbit signals intelligence spacecraft and communications satellites to support US intelligence-gathering. Two other launches carried the mysterious PAN and CLIO satellites, for which no government agency has acknowledged responsibility.

Environmental research missions launched on behalf of the National Oceanic and Atmospheric Administration (NOAA) have included five weather satellites; placing the NOAA-19 and Suomi NPP satellites into polar orbit and three Geostationary Operational Environmental Satellite (GOES) into geosynchronous orbit. ULA also launched the Franco-American Jason-2 ocean research satellite, atop a Delta II in June 2008.

ULA conducts commercial missions on behalf of Boeing and Lockheed Martin. Between 2007 and 2010 four Delta IIs were used to launch Italy’s COSMO-SkyMed imaging constellation. Delta II and Atlas V rockets have also been used to launch the commercial WorldView 1 to 4 and GeoEye-1 imaging satellites.

On the East Coast, three commercial Atlas V launches have been conducted with geosynchronous communications satellites; ICO-G1 in April 2008, Intelsat 14 in November 2009 and Morelos-3 in October 2015 – the latter being ULA’s hundredth launch.

Going into its next ten years, United Launch Alliance is developing a new rocket, Vulcan, which is intended to replace both the Atlas V and Delta IV. To this end, ULA has begun the process of retiring the Delta IV; with all Medium configurations expected to be out of service by 2018.

The Delta IV Heavy will remain in service until another rocket is available to replace it. Separately, the final flight of the Delta II rocket is currently scheduled for next November.

Wednesday’s launch used Delta 376. Its Medium+(5,4), or M+(5,4) configuration consisted of a single Common Booster Core (CBC) first stage, a five-metre diameter Delta Cryogenic Second Stage and four GEM-60 solid rocket motors to provide additional thrust at liftoff.

This is the configuration that has been used to launch the five most recent WGS satellites, after the first two satellites flew aboard the Atlas V. Like the rocket which launched WGS-7, Delta 376 sported an upgraded RS-68A first stage engine instead of the RS-68 that the Delta IV was originally designed to use.

First introduced on the Delta IV Heavy, the RS-68A has now supplanted the RS-68 across all of the Delta IV configurations that remain in service. The core stages of the Delta IV burn cryogenic propellant; liquid hydrogen oxidized by liquid oxygen.

Delta 376’s launch began with first stage ignition, five seconds ahead of the planned liftoff. Once the countdown reached zero, the solid rocket motors ignited and Delta 376 began its ascent towards orbit. Seven seconds after liftoff the vehicle began a series of pitch, yaw and roll maneuvers to put itself on course for the ascent to orbit. Delta flew a launch azimuth of 93.46 degrees, East out over the Atlantic.

Climbing through Earth’s atmosphere, Delta 376 passed through the area of maximum dynamic pressure, or Max-Q, 46.2 seconds into flight.

The first pair of solid motors burned out 91.6 seconds after liftoff, followed by the second pair a second and a half later. The spent casings remained attached for a few seconds, before being jettisoned in pairs 2.4 seconds apart, beginning 100 seconds after launch.

Three minutes and 14.4 seconds into Wednesday’s mission, the payload fairing separated from around the WGS-8 satellite at the nose of the Delta IV. The first stage continued to burn until three minutes and 56 seconds mission elapsed time, at which point the RS-68A was shut down. Six seconds later the spent Common Booster Core separated from the vehicle.

The Delta IV’s second stage, or Delta Cryogenic Second Stage (DCSS) is powered by a single RL10B-2 engine. This has an extendible nozzle which deployed after separation. The engine ignited thirteen seconds after staging to begin the first of two second stage burns. The first burn lasted fifteen minutes and 36.8 seconds.

The coast phase between the end of the first upper stage burn, and the beginning of the second, lasted nine minutes and 34.8 seconds. Following the coast, the RL10 engine restarted for three minutes and seven seconds, to reach the target deployment orbit for WGS-8.

The satellite separate, at 41 minutes, 43.6 seconds mission elapsed time, into a 435 by 44,378 kilometer (270 x 27,575 miles; 235 x 23,962 nautical miles) geosynchronous transfer orbit at an inclination of 27 degrees. Following spacecraft separation, the DCSS performed a third burn to deorbit itself.

Wednesday’s launch was the fourth and final Delta IV launch of 2016, following launches in February and June for the National Reconnaissance Office that carried a Topaz radar imaging satellite and an Orion signals intelligence satellite as part of the NROL-45 and NROL-37 missions respectively. In August, another Delta IV launched the second pair of GSSAP space surveillance satellites.

The launches in 2016 have used each of the four active Delta IV configurations, with NROL-45 using a Medium+(5,2), NROL-37 using a Heavy, GSSAP using a Medium+(4,2) and WGS a Medium+(5,4). The Delta IV’s fifth configuration, the Delta IV Medium, is effectively retired as the medium-class configurations have been discontinued and it has no outstanding launches.

The next Delta IV launch is currently scheduled for March, with WGS-9, which will also be the next Wideband Global Satcom spacecraft to fly.

The WGS-8 mission was the eleventh of the year for ULA, who have one more scheduled. That is currently expected to occur on 16 December, when an Atlas V will perform a commercial launch on behalf of Lockheed Martin, carrying the EchoStar XIX satellite. Before then there will be another launch from Cape Canaveral, with Orbital ATK’s Pegasus-XL rocket due to loft NASA’s CYGNSS mission on 12 December.